The present invention relates to printing devices. More particularly, the present invention relates to an apparatus and method for transporting print media through a printzone of a printing device.
Printing devices, such as inkjet printers and laser printers, use printing composition (e.g., ink or toner) to print images (text, graphics, etc.) onto a print medium in a printzone of the printing device. Inkjet printers may use print cartridges, also known as xe2x80x9cpensxe2x80x9d, which deposit printing composition, referred to generally herein as xe2x80x9cinkxe2x80x9d, onto a print medium such as paper, labels, forms, or transparencies. Each pen has a printhead that includes a plurality of nozzles. Each nozzle has an orifice through which the printing composition is ejected. To print an image, the printhead is propelled back and forth across the print medium by, for example, a carriage while ejecting printing composition in a desired pattern as the printhead moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as thermal printhead technology. For thermal printheads, the ink may be a liquid, with dissolved colorants or pigments dispersed in a solvent.
Printing near the bottom margin of a print medium being transported through a printzone of a printing device can be difficult. Vacuum platens in the printzone have been proposed and implemented as a means for controlling print medium flatness in the printzone. These designs employ a fixed vacuum platen which did not address bottom margin printing performance. Vacuum belts and drums have been proposed to control print media shape and improve bottom margin printing performance. These solutions are expensive, however, because of the materials needed for the belt or drum and the large motors required to pull the belt over a vacuum zone or rotate the drum.
Star rollers are a proposed solution for improved bottom margin printing performance. These star rollers do not employ the use of a vacuum belt or drum. The star rollers are located downstream of the drive rollers, pinch rollers, and printzone. These star rollers pull a print medium through the printzone so that the printing can occur near the bottom margin of print media. Problems exist, however, with the use of star rollers. Star rollers can cause permanent damage by punching holes through a print medium. Additionally, star rollers can smear images on a print medium where they come into contact with the images. Furthermore, print medium line feed artifacts can occur as the drive rollers and pinch rollers, which push print media through the printzone, handoff transport of print media to the star rollers, which pull print media through the printzone.
An apparatus and method directed to these above-described problems associated with bottom margin printing would be a welcome improvement. Accordingly, the present invention is directed to an apparatus and method for transporting print media through a printzone of a printing device that addresses the above-described problems associated with bottom margin printing.
An embodiment of an apparatus in accordance with the present invention for transporting print media through a printzone of a printing device includes a print media movement mechanism configured to advance a first portion of a print medium through the printzone. The apparatus additionally includes a translating vacuum platen downstream of the print media movement mechanism to receive the print medium and configured to convey a remaining portion of the print medium through the printzone.
The above-described embodiment of an apparatus in accordance with the present invention may be modified and include at least the following characteristics, as described below. The print media movement mechanism may include at least one drive roller and at least one pinch roller. The translating vacuum platen may include a solenoid drive mechanism. Alternatively, the translating vacuum platen may include a cam drive mechanism. As another possible alternative, the translating vacuum platen may include a rack and pinion drive mechanism. As a further possibility, the translating vacuum platen may include a pneumatic cylinder drive mechanism.
An embodiment of a method in accordance with the present invention for use in a printing device having a printzone in which printing composition is deposited on print media includes advancing a first portion of a print medium through the printzone. The method additionally includes acquiring the print medium via a vacuum hold-down force. The method further includes translating a remaining portion of the print medium through the printzone via the vacuum hold-down force to enable deposition of printing composition at a bottom margin of the print medium.
An alternative embodiment of a method in accordance with the present invention for use in a printing device having a printzone includes transporting a first portion of a print medium through the printzone. The method also includes printing on the first portion of the print medium. The method additionally includes releasing the print medium subsequent to printing on the first portion. The method further includes conveying a remaining portion of the print medium through the printzone and printing on the remaining portion of the print medium.
An alternative embodiment of an apparatus in accordance with the present invention for use in a printing device having a printzone includes a drive roller and a pinch roller mechanism configured to transport a print medium through the printzone. The apparatus additionally includes a vacuum platen positioned in the printzone of the printing device to receive the print medium from the drive roller and pinch roller mechanism. The apparatus further includes a drive mechanism coupled to the vacuum platen to translate the vacuum platen and print medium thereon to enable printing at a bottom margin of the print medium.
The above-described alternative embodiment of an apparatus in accordance with the present invention may be modified and include at least the following characteristics, as described below. The drive mechanism may include a solenoid. Alternatively, the drive mechanism may include a cam. As another possible alternative, the drive mechanism may include a rack and pinion gear. As a further possible alternative, the drive mechanism may include a pneumatic cylinder.
Another alternative embodiment of an apparatus in accordance with the present invention for use in a printing device having a printzone and a printing mechanism for printing on print media includes structure for transporting a first portion of a print medium through the printzone. The apparatus also includes vacuum hold-down structure for acquiring the print medium from the structure for transporting. The apparatus further includes structure for moving the vacuum hold-down structure to convey a remaining portion of the print medium through the printzone so that the printing mechanism can print at a bottom margin of the print medium.
The foregoing summary is not intended by the inventors to be an inclusive list of all the aspects, advantages, and features of the present invention, nor should any limitation on the scope of the invention be implied therefrom. This summary is provided in accordance with 37 C.F.R. Section 1.73 and M.P.E.P. Section 608.01(d). Additionally, it should be noted that the use of the word substantially in this document is used to account for things such as engineering and manufacturing tolerances, as well as variations not affecting performance of the present invention. Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.